This application claims the priority of Korean Patent Application No. 2001-73017 filed 22, Nov. 2001, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a plasma flat lamp, and more particularly, to a plasma flat lamp having a high luminance, a high efficiency of light emission, and a uniform distribution of luminance.
2. Description of the Related Art
Flat lamps mainly used as back-lights of LCDs have been developed into surface discharge type or facing electrodes discharge type plasma lamps, in which the entire space under a light emitting surface makes a discharge space considering the efficiency of light emission and uniformity of luminance of light emission, from the conventional edge-light or direct-light type plasma lamps using a cold cathode fluorescent lamp.
In general, the surface discharge type is advantageous in that a discharge feature is stable compared to the facing electrodes discharge type. However, the overall luminance of the surface discharge type is lower than that of the facing electrodes discharge type. As an example of a conventional surface discharge flat lamp, there is a lamp in which the overall discharge space is divided into fine discharge areas to prevent local concentration of discharge. This lamp can discharge stably. However, since the uniformity of the overall luminance of light emission is inferior due to a difference in the luminance of light emission between the fine discharge areas and a gap between the fine discharge areas, a diffusing paper or diffusing plate is needed to uniformly diffuse light (M. Ilmer et al., Society for Information Display International Symposium Digest of Technical Papers 31, 931 (2000)).
FIG. 1 shows another example of the conventional surface discharge type flat lamp. A discharge space filled with a discharge gas is formed between an upper plate 1 and a lower plate 2 separated by a wall portion 7. Electrodes 3 and 4 for discharge are formed at both sides of an inner surface of the lower plate 2. A dielectric layer 5 is formed on each of the electrodes 3 and 4. A fluorescent layer 6 is formed on each of the inner surfaces of the upper and lower plates 1 and 2. The conventional surface discharge type flat lamp having the above structure has been known to have a low luminance due to its discharge characteristic (Y. Ikeda et al., Society for Information Display International Symposium Digest of Technical Papers 31, 938 (2000)).
FIG. 2 shows an example of the conventional facing electrodes discharge type flat lamp. An upper plate 1a and a lower plate 2a are separated a predetermined distance from each other by a wall portion 7a and a discharge space is provided therebetween. Electrodes 3a and 4a for discharge are formed on inner surfaces of the upper and lower plates 1a and 2a to face each other. A fluorescent layer 6a is formed on each of the electrodes 3a and 4a. The upper and lower plates facing electrodes discharge type flat lamp having the above structure has a high luminance compared with the surface discharge type flat lamp shown in FIG. 1, but has a low efficiency of discharge and an unstable discharge due to excessive current (J. Y. Choi et al., Proceedings of the 1st International Display Manufacturing Conference, 21 (2000)).
FIG. 3 shows yet another example of the conventional facing electrodes discharge type flat lamp. Electrodes 3b and 4b are formed to face each other on inner surfaces of a wall portion 7b facing each other. Each of the electrodes 3b and 4b is protected by a dielectric layer 5b. Upper and lower plates 1b and 2b are separated by the wall portion 7b. A discharge space in which a discharge between the electrodes 3b and 4b is induced is provided between the electrodes 3b and 4b. A fluorescent layer 6b is formed on each of inner surfaces of the upper and lower plates 1b and 2b. The side wall portion facing electrodes discharge flat lamp having the above structure can prevent excessive current. However, discharge is unstable, in particular, discharge tends to concentrate on a local point.
As described above, in the conventional flat lamps, it is disadvantageous that either luminance is low while discharge is stable or luminance is high while discharge is unstable.